The present invention is directed to a vibratory feeder. More particularly, the present invention is directed to a vibratory feeder with improved adjustability. Vibratory feeders using twin sets of leaf springs are known. At least one patent has suggested substituting an elastomeric spring for one of the sets of leaf springs. The problem with the embodiment taught in this patent is that the elastomeric spring acts in compression. Compressed rubber tends to creep, that is, as the force continues to be exerted, over time, the rubber will “submit” to the pressure and move away from the source. Tests on this type of elastomeric spring have shown a wide range of values for the spring rate for the elastomeric spring and, consequently, large variation in the feed rate for the vibratory feeder. When used by a manufacturer who measures quantities using a scale, such variations are totally unacceptable with wide variations in speed and performance. Adjusting the “spring constant” on such a compressive spring requires constant vigilance to maintain the desired flow rate.
The adjustable vibratory feeder of the present invention, available from the assignee as the HS-8 Feeder, addresses these problems by providing a highly stable elastomeric spring. The improved elastomeric spring includes a first elastomeric shear pad extending generally parallel to the primary excitation plane of the moving mass; a second elastomeric shear pad extending generally parallel to the primary excitation plane of the moving mass; a support for the moving mass extending in the primary excitation plane of the moving mass and being sandwiched by the first and second elastomeric shear pads; means to adjust a compressive force exerted by the first and second elastomeric pads on the support for the moving mass to vary a spring rate of the first and second pads and thereby adjust a feed rate of the vibratory feeder system. The elastomer used in the first and second pads is, itself, highly stable. Tests on a feeder employing the elastomeric spring of the present invention showed less than 3% variance over a 40 hour period of operation.
Various other features, advantages, and characteristics of the present invention will become apparent after a reading of the following detailed description.